Shock absorber



Nov. 29, 1938. w. c. ROBBINS SHOCK ABSORBER Filed Maron 1x61l 1938 a a 2 @ya 4 7 64 w H m 7 E 0 6 04 3 44 63 42 4 44M6 0 6M 3. f s 6 2 Z M 4 6 z mx w m 2 Patented Nov. 429, 1 938 l 2, l l 1 UNITED STATES PATENT OFFICE SHOCK ABSORBER ,Walter C. Robbins, Bridgeport, Conn., assigner to Frank P. Scully, Cambridge, Mass., and Harry B. Curtis, Bridgeport, Conn., as trustees Application March 16, 1938, Serial No. 196,188 5 Claims. (Cl. 188-88) The present invention relates to shock arm 26, which is attached in the. usual manner absorbers of the fluid type, and is more particuto the axle or movable part or other portion of larly concerned with fluid shock absorbers of the the chassis of a motor vehicle or whatever else type shown generally in. the patent to McNab it may be desired to check.

5 No. 1,855,921, dated April 26, 1932. The shaft I6 is provided intermediate the In this type of shock absorber which is probearings with a series of longitudinal and parallel vided with the usual huid-tight casing and proteeth 28, which slidingly receive a piston desigjecting oscillatory arm for connection to an axle nated generally at 30 through the provision of a or the like, a piston is slidingly keyed to the arm centrally disposed opening which fits the toothed shaft and is caused to traverse lengthwise of the or ribbed surface. The outer peripheral portion l0 fluid chamber upon oscillation of the shaft by of the piston is provided with helically disposed virtue of helical grooves engaging with correteeth or ribs 32 which mesh with correspondingly sponding teeth on the piston and forming in efformed helical grooves 34 in a sleeve 36. fect a lead screw f'or traversing the piston an With this construction oscillatory movements amount determined by the amplitude of oscillaof the shaft I6 impart similar movements to the 15 tion. The movement of this piston compels fluid piston 36, which are converted into longitudinal ow from one side of the piston, to the other as traversing movements of the piston through engoverned by a restricted orifice, the oricial regagement with the helical traversing grooves. striction serving to check and retard movements The curved sleeve or liner 36 may preferably be of the oscillating arm particularly on rebound. cast in a form such as a die casting and assem- 20 It is the object of the present invention to imbled within the cylindrical portion of the housing prove and reorganize Huid shock absorbers of this l. The sleeve is locked in place within the housgeneral type in order to insure an efficiently ing by a key 40 seated in a slot 4I formed in the operating mechanism which can be manufactured wall of the sleeve, as indicated in Figs. 1 and 2.

within practical limitations of cost, and to pro- When assembled within the housing a partition 25 vide automatic control for fluid ow governed disk 42 divides a fluid reservoir 44 from the adin accordance with changes in viscosity of the jacent fluid chamber 46, the second fluid chamber fluid due to rising and falling temperatures. being indicated at 48 at the opposite side of the With these and other objects in view, the varisliding piston, this chamber being closed by a ous features of the invention consist in certain stationary wall provided through the closure 20 30 novel features of construction, combinations and and a sealing plate 50. arrangements of parts hereinafter described and I have found by practical experience that great claimed, the advantages of which will be obvious difficulty is experienced in providing for an adeto those skilled in the art from the following de'- quate seal between the periphery of the piston scription. and the lining sleeve on the one hand, and the 35 In the accompanying drawing illustrating the hub or inner portion of the piston and the splined preferred form of the invention, Fig. 1 represhaft on the other, if these several parts are sents an elevation in section of the shock absorber fabricated in the normal fashion, first because with the outer end of the arm broken away; the tolerances must be exceedingly small to pre- 40 Fig. 2 is a section in p-lan takenv upon the line vent undue leakage, and secondly because With 40 2 2 of Fig. l; and Fig. 3 isa detail of the recipr these comparatively low allowable tolerances the eating piston slidingly keyed to the operating cost of the construction is greatly increased, and shaft. in addition unusual wear of the contacting sur- The shock absorber disclosed in. the illustrated faces results with a comparatively short tenure embodiment of the invention comprises generally of useful life. According to the present invention 45 a housing l El, having a drilled attaching iiange l2 1' have found that by constructing the piston with and a fluid replenishing plug if. Supported cencomplementary steel or equivalent metal sections trally of the housing and extending therethrough or portions, each having the peripheral helical is an oscillatory shaft iii, journaled at its end teeth and hub splines, and by interposing be.-

remote from the arm in a closed bearing i8 tween these complementary portions an inner 50 formed in a closure plate 2Q, which is threadedly section or member of leather or its equivalent mounted in the housing as indicated in Fig. 1. having corresponding teeth and splines to register The shaft iii at its opposite end projects through with those of they metallic portions, satisfactory an oil-retaining seal 22, and is splined at its sealing may be accomplished without the necessity outer end 24 to receive the hub of a connecting of close tolerances and. with a resulting long 55 tenure of life, particularly if provision is made for the flow of lubricating fluid between the contacting surfaces of the. leather cushion and the opposing metallic` heads- To this end it will be observed, as shown more particularly in Fig. 3, that I provide complementary portions 52 and 54, each being fashioned with the necessary grooves and splines, and that I interpose between these members upon assembly a similarly fashioned layer of leather or equivalent cushion material 55. With the parts fastened in any appropriate fashion, I have found not only that leakage is.

avoided even though a loose fit is adopted, and that the piston will function satisfactorily with the sleeve 35 of die cast material or other material softer in composition than that of the piston. For effecting additional lubrication between the metal portions of the piston and the leather inner portion, I provide openings 58 through which seepage or circulation of lubricating fluid is accomplished. 'I'he piston is also p-rovided with one or more through openings. 6G, each provided with a ball check valve 62, which in the illustrated embodiment of the invention checks the ow of oil from right to left, or in other words, from the chamber 48 into the chamber 4%, but freely permits the flow of oil in the opposite. direction. In addition, fluid flow from the replenishing chamber 44 into the adjacent working chamber 46 is permitted through a. ball check 64. located in a housing 6B mounted in the partition member 42, this ball check being designed to permit free replenishment, but to prevent return from the working chamber into the replenishing chamber.

This type of construction permits a comparatively largequantity of fluid to be displaced with small movements of the arm, a movement on the order of to 100 of the arm accomplishing substantiallyA a complete traverse of the working chamber by the piston. Due to the relatively large amount of fluid moved thereby, the instrument with comparatively small over-all dimensions can be made to satisfactorily serve the shock absorbing function without generating extremely high pressures within the shock absorber and requiring in consequence strengthening safeguards. The capacity in a small instrument to handle necessary movements with measurably lower fluid pressures is an important and desirable aspect of this type of shock absorber.

It will be observed from an inspection of Figs. l and 2 of the drawing that longitudinal traversing movements of the piston 3G compel a ilow of liquid from the chamber 46 to the chamber 48y or vice versa. This is accomplished through the provision of huid passages 65 and 61 leading respectively from the working chambers 44 and 48 into the hollow bore 59 of the arm shaft. As will be noted from the drawing, these openings in each case are drilled through the splined hub 2.3 of the shaft i6, and form in effect a single opening moving with the oscillatory motion of the shaft and in constant communication with both the working chambers and the hollow bore of the shaft. In order to control the shock absorbing function, fluid flowing from one chamber to the other is caused to pass through an. orifice of' predetermined dimensions and characteristics. In order to compensate for the effects of varying temperatures upon the viscosity of the fluid, it is necessary to modify the character of the orifice in accordance with changes of temperature or fluid viscosity, and to this en'd I provide within the hollow bore of the shaft I6 a sleeve valve 'l0 mounted in the bore at the end of the shaft and having a tapered slot or opening l2 which is metered by the advanced edge of an inner sleeve 14, as will be evident from Fig. l. The sleeve 14, which constitutes the movable element of the valve, is slidingly mounted within the interior of the shaft, and is providedwith openings 16 to afford communication with the port 65. This movable sleeve is connected in any suitable manner to the free end of a bellows thermostat 'I8 for movement therewith in both directions. The thermostat is provided with a guiding head 8i) and is anchored at its opposite end by virtue of a stud or plug 82 threaded within the shaft. The

bellows thermostat is normally filled with a liquid similar in its characteristics to the fluid within the shock absorber, and expanding and contracting with changes in temperature which affect the shock absorber fluid. As the temperature rises the fluid within the bellows expands, causing a like expansion of the thermostat, with a movement from left to right of the sleeve valve. This movement cuts down the size of the orifice 'l2 and compensates for the greater fluidity or decreased viscosity of the fluid at the higher temperature. As the temperature drops, the bellows thermostat a like manner contracts, exposing a larger orifice to fluid of increased viscosity. It

possible by proper control of they size of the orifice with this type of compensation to secure virtually a straight-line resistance of the shock absorber regardless of temperature conditions. It will be noted that a return spring @il is provided for insuring return of the bellows and connected valve upon contraction of the fluid therein. The outer end of the shaft beyond the. inserted plug maybe closed by a cap 92, the plug itself being adjustable to vary the anchor point of the bellows thermostat and regulate the size of the control orifice and in consequence the resistance of the shock absorber within any given range.

What is claimed is:

1. A shock absorber, comprising a casing having a fluid chamber therein, a hollow shaft extending into the chamber, an arm connected to the shaft, a piston keyed to the shaft to oscillate therewith, connections between the piston and the peripheral wall of the chamber to cause oscillatio-n of the piston to traverse the latter lengthwise of the chamber, uid passages connecting the longitudinal bore of the shaft with the fluid chamber at opposite sides of the piston, a fixed valve having a metering port mounted in the hollow bore of the shaft, a sleeve slidingly received within the valve-to adjust the exposure of the port, a bellows thermostat seated within the hollow bore of the shaft and connected with the sleeve to move the latter in accordance with temperature changes, fluid openings in the sleeve to cause passage of fluid therethrough, and means for anchoring one end of the bellows thermostat lengthwise of the shaft.

2. A shock absorber, comprising a casing having a fluid chamber therein, a die cast linerV ing a uid chamber therein, an oscillatory shaft extending within the iluid chamber, a piston comprising an inner portion of cushion material clamped between outer metallic portions, the composite piston being slidingly keyed to the shaft and having peripheral teeth formed thereon, and helical grooves at the periphery of the uid chamber engaging With the piston teeth to produce longitudinal movement of the piston upon oscillation thereof.

4. A shock absorber, comprising a casing having a uid chamber, an operating shaft, a piston comprising complementary metal portions each having peripheral helical teeth, an inner cushion portion having similar teeth clamped between the complementary portions to form when assembled continuousI helical teeth, and a liner secured to the casing and having helical grooves formed therein meshing With the teeth of the piston.

5. A shock absorber, comprising a casing having a uid chamber therein, an oscillatory shaft, a liner having traversing grooves secured to the casing, and a piston comprising complementary metallic portions and an inner leather portion, the various portions be-ing formed in such a manner that When assembled complete helical teeth are formed at the periphery, the piston, being slidingly keyed to the shaft, and openings through the complementary portions for the circulation of lubricating fluid therethrough to the inner leather portion.

WALTER C. ROBBINS. 

